C.E. Niehoff & Co. C672 Troubleshooting Guides - Manual (Page 4)

Page 4 TG73A
LED COLOR STATUS
TABLE 2 — A2-342 Regulator LED Diagnostics with Engine On*
Alternator and regulator operating normally. GREEN Solid
Low system voltage — Electrical load exceeds
alternator rating at present rotor speed.
ACTION
No action required.
When loads decrease or speed increases, LED
should be solid GREEN. If not, check drive belt and
charging system connections.
Replace alternator.*
AMBER Solid
High system voltage – May occur during
normal load switching.
Indicates voltage above setpoint but below OVCO
threshold (less than 33 volts).
Indicates voltage exceeds 33 V for more than
3 seconds. System diagnosis required. See OVCO
condition in “General Troubleshooting” section
below.
RED Solid
Alternator fault — No output.* Flashing*
Flashing OVCO tripped.
General Troubleshooting
OVCO condition
Shut down vehicle and restart engine. If alternator functions normally after restart, a “no output condition” was normal
response of voltage regulator to “high voltage” condition. Inspect condition of electrical system, including loose battery
cables, both positive and negative. If battery disconnects from system, it could cause “high voltage” condition in electrical
system, causing OVCO circuit to trip.
If you have reset alternator once, and electrical system returns to normal charge voltage condition, there may have been
a one time, high voltage spike, causing OVCO circuit to trip.
If OVCO circuit repeats cutout a second time in short succession and shuts off alternator field circuit, try third restart.
If OVCO circuit repeats cutout, check that pin F in alternator-to-regulator harness is not shorted to B+ terminal on
alternator and that pin A in alternator-to-regulator harness is not shorted to B–. If it is shorted, alternator is defective.
If not, regulator is defective.
Section C: On-Vehicle Troubleshooting
A2-342 Regulator Troubleshooting
Main diagnostic feature is a tricolored LED located on the front of the regulator. LED works like a voltmeter, measuring
charging voltage. See Table 2 for LED diagnostics.
This regulator has OVCO (overvoltage cutout) that will trip at vehicle electrical system voltage above 33 volts that exists
longer than 3 seconds. OVCO feature detects high voltage and reacts by signaling relay in alternator field circuit to open.
This turns off alternator (LED is flashing RED). OVCO circuit is reset when engine is restarted or can also reset when
system voltage normalizes after 2-minute wait.
An optional temperature/voltage sense/J1939 harness may or may not be used with the regulator:
• When temperature/voltage sense/J1939 harness is not connected, regulator will operate in fixed voltage setting
determined by the select switch position on the bottom of the regulator.
• When temperature/voltage sense/J1939 harness harness is connected, regulator will automatically optimize the charge
voltage for battery type selected based on temperature. Also, vehicle manufacturer-requested functions of 1939
interface are available through connector.
No power to ignition or regulator is defective. OFF Go to Chart on page 5.
* LED will flash AMBER for one minute upon start-up/shutdown—if regulator does not sense alternator rotation, regulator will time out.